Adding Data in Grid colums. (Not to row specific)

HI Guys,

I have a requirement as show in the below image..

Select.png
As the user will keep selecting the checkbox in the grid panel. i need to populate the selected options as shown above.
Kindly note this is not adding a entire row,but i need to add the data to the specified columns under the specific family code as shown above dynamically.ie.,, if the user selects a more option in the primary then i need to populate the values on check box click and remove them on the deselection.

i am not too much well versed in ExtJs, so kindly give me a heads up on
Q1. How can i add a value to the column in the grid.
Q2. is this wrong approach to use a grid. is template a better solution for this.(not i have to add this dynamically)
Q3. And if i can make a treegrid. how to add a data in the specific column
Q4. Please help